ADC fixed reference

Rasik

Prodigy 175 points

Hello,

Basically wanted to enhance resolution of internal ADC (range of input is not the constraint)

Lowering the reference voltage (< fixed 4.3V) is one of the way.

Using the 'VTRIM' settings (in REF1 register) is the right way for that ?

What "nominal voltage" specifies in the VTRIM settings ?

Regards

over 10 years ago

0 Christin Lee over 10 years ago

TI__Guru 56215 points

yes, you can move the VTrim to a lower setting, and the nominal voltage is set to 1.48V.

0 Rasik over 10 years ago in reply to Christin Lee

Prodigy 175 points

Hi,

Nominal voltage is set to 1.43V & not the 1.48V ?

Regards.

0 Rasik over 10 years ago in reply to Rasik

Prodigy 175 points

Hi,

Since reset value of ADCREF1 is 0x00 & this means nominal voltage is 1.43V, then will the VTRIM settings will be applied by default ?

Therefore, ADC will have fixed reference of 4.3V or 1.43V ?
To apply VTRIM settings, 'EN' (ADCREF0:0) should be 1 ?

Regards.

0 svendbt over 10 years ago

TI__Mastermind 29650 points

Hi Rasik,

The ADC reference is trimmed to its correct values by the device trim (driverLib/setup.c - trimDevice) which is executed before main().
Users should not re-write this register manually (the trim range is anyway quite small).

Our only option to reduce range is to disable the ADC scaling which scales input voltages between GND and VDDS to within GND and internal reference. This requires the input voltage to never exceed 1.49V as described in "Absolute maximum ratings" in the data sheet.

Let me know if this is a feasible option in your case.

Regards,
Svend

0 Abhijeet Kanade over 10 years ago in reply to svendbt

Intellectual 630 points

Hello Svend,

I just wanted to know how to disable adc scaling?

Do we have any api to disable scaling?

Regards,

Abhijeet

0 Christin Lee over 10 years ago in reply to Abhijeet Kanade

TI__Guru 56215 points

Please find TRM section 17.4.8.4

0 Kimi Hu over 9 years ago in reply to Christin Lee

Mastermind 6105 points

Hi Christin,

From TRM section 17.4.8.4. ADI_4_AUX:ADC1.SCALE_DIS only to be used through TI provided API. Can you tell me which API can modify this register? thanks

0 Christin Lee over 9 years ago in reply to Kimi Hu

TI__Guru 56215 points

You can find the API in driverlib, aux_adc.h
AUXADCDisableInputScaling()

0 Kimi Hu over 9 years ago in reply to Christin Lee

Mastermind 6105 points

Hi Christin,

Thank you for your help.

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ADC fixed reference